In a withering editorial published on Sunday, the Roman Catholic Archdiocese of Mexico said that Mexican firms interested in helping build President Donald Trump's proposed border wall are "traitors to the homeland."

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"It is not two or three, but more than 500 companies," from Mexico expressing interest in Trump's proposed border wall, the editorial says. "For them, the end justifies the means."

Building a wall along the nearly 2,000-mile U.S. border with Mexico was estimated by congressional Republicans to cost $12 billion to $15 billion. An internal report prepared for Homeland Security Secretary John Kelly estimated that a wall along the entire border would cost about $21 billion, according to the Associated Press.

After repeatedly claiming that Mexico would pay for the wall, President Trump requested $2.6 billion to start the initial planning and construction in his 2018 budget request. Congress is expected to take up the proposed budget before the end of the fiscal year in September.

The editorial, published in the Archdiocese's weekly publication Desde la fe, lambasted the wall as "an open threat that violates relations and peace."

Trump made building a wall on the southwestern border a centerpiece of his 2016 campaign, saying he wants a concrete barrier as high as 55 feet tall that he has described as "impenetrable, physical, tall, powerful, beautiful."

The wall has sparked backlash in Mexico, where leaders have spoken out against it publicly. Mexican President Enrique Peña Nieto has said his country will not pay for "any" wall on the U.S. border and said he rejects Trump's decision to go ahead with the plan.

Economy Secretary Ildefonso Guajardo warned last week that Mexican citizens would judge companies who choose to participate and base future buying decisions on "which brands are loyal to the national identity, and which are not," according to the Associated Press.

"Joining a project that is a serious affront to dignity, is to shoot yourself in the foot," the Archdiocese editorial reads. "The wall is a monument of intimidation and silence, of xenophobic hatred."

"Any company with the intention to invest in the wall of the fanatic Trump would be immoral, but above all, its shareholders and owners should be considered traitors to the homeland," the editorial concludes.